PTL 1 discloses a conventional transformer including a multilayer board having coils provided therein. In a printed coil type transformer disclosed in PTL 1, five base materials are stacked, and a core made of magnetic material passes through centers of these base materials. A secondary coil is provided on a front surface and a rear surface of the first layer out of the base materials. The secondary coil is also provided on each of a front surface and a rear surface of the second layer out of the base materials. A primary coil is provided on each of a front surface and a rear surface of the fourth layer out of the base materials. The primary coil is also provided on each of a front surface and a rear surface of the fifth layer out of the base materials.